Method of vulcanizing rubber and resulting products



Patent ed Nov.- 1929 UNITED STATES HENRY B. MORSE, OF DANVERS,MASSACHUSETTS, A SSIGNOR, BY MESNE ASSIGNMENTS,

PATENT OFFICE TO ALBERT O. BURRAGE, JR., IPSWICH, MASSACHUSETTS METHODOF VULCANIZING RUBBER AND RESULTING PRODUCTS no Drawing;

This invention relates to the art of treating rubber or rubbercompounds, and has for an object the provision of an improved procedurefor the vulcanization of the same in 5 the presence of an acceleratorand of compounds or compositions with which to effect the purpose of theinvention.

In the art of rubber manufacture, it has long been known that thevulcanizing process 10 may be, accelerated by the addition of various 2oThose selectedfor(practical use, however, are

generally restricte to compounds which may be mixed with the rubberorrubber compound w-ithout inducin appreciable vulcanizing effect atatmospheric temperature or during milling operations, but which activitaccelerate the reaction in the customary vu canizing treatment. Otheraccelerator compounds, frequently termed ultra accelerators ofsemi-ultra accelerators, initiatethe vulc izing reaction sometimesprematurely, either in the cold only orduring the mixing operation,resulting in scorching which hinders or entirely prohibits the furtheruse of the rubber or rubber-compound.

Consequently, such compounds ordinarily have not been used in themanufacture of rubber products, even though they would greatly reducethe time 6 uired for vulcanization and may be otherwlse suitable for use40 in rubber compositions.

By the present invention it is found that the acceleratin action ofaccelerator compounds genera ly in rubber compositions,

may be inhibited (at ordinary and slightly elevated temperatures anddurmg themixing and milling operations) or retarded by the addition oforganic compounds of a certain type hereinafter defined, and thatthereafter the vulcanizing reaction,effectively accelerated by theaccelerator,- may' be caused Application filed June 4, 1928. Serial110,868,430;

1 to proceed at will by subjecting the rubber compositlon to bevulcanized to vulcanizing conditions.

It is thought that the accelerator and the inhibitor react or combine toform a reaction product or compound which doesnot promote thevulcanizing reaction of the vulcanizable composition (under thepreliminary conditions such as mixing and milling) but I which, underthe vulcanizing conditions such as increased. temperature, dissociatesand liberates the accelerator which then acts in its acceleratingcapacity, and the inhibitor may remain inert or may itself act as anaccelerator. i

In other words, the critical temperature of. the accelerator, withrespect toits initiating prematurely the vulcanizing reaction in therubber,'is apparently raised to a point above the temperatures ofmilling or compounding and within the range of the vulcani'zingtreatment. f

The compounds manifesting such inhibiting action upon prematureinlt-iation of vulcanization by accelerators (and more especially theltra accelerators and those sometimes referred to as semi-ultraaccelerators-among which may be mentioned, the thiazoles, represented bymercapto benzo thiazole, certaindisulfides' such as tetra methyl thiuramdisulfide, certain monosul fides; such as tetra methyl thurammonosulfide, etc., and their derivatives) are found Q to typicallyinclude the nitroso-amines which may be represented by the empiricalformula:

in which R and R represent alkyl or aryl radicals. (or nuclei) which maybe alike or unlike and in turn may contain or be asso' ciated with oneor more substituents.

While the substituted nitroso-amines, as thus defined, may containsubstituents which are alike, they may also contain substituents whichare different or unlike. Thus the substituents R and R may bearylradicals and may furthermore be associated with or c-onl tain otherhydrocarbon radicals or nuclei.

For example, one substituent may be an unsubstituted aryl group and theother a na hthyl group, as m phenyl beta napht yl nitroso-amine' In arepresentative example of the invention,rubbe'r' and the usualvulcanizing and 'to or better than that obtained withoutthe use of thepreliminary inhibiting compound or prehibitor.

In a preliminary scorching? test, for example, in which the compoundswere subjected to especially high temperatures during the mixing andmilling operations until scorching was effected, a rubber compositioncontaining: 4 100 parts rubber (smoked sheet) 3% parts sulfur 5 partsZnO 'part mercapto benzo thiazole' to which .43 part dibeta naphthylnitrosoamine was added, was thoroughly milled and mixed on the mixingrolls; the mix was then removed'and again milled on rolls, purposelyheated by steam so as to maintain a temperature in the stock ofapproximately 95 to- 100 C.,-for 110 minutes before scorching occurred.

A correspondin stock without the addition of dibeta naphthynitroso-amine, upon being milled and mixed, and again milled under likeconditions of temperature, scorched in 65 minutes.

A similar test carried out upon a rubber 4 compound of the formula:

100 parts rubber (smoked sheet) 3 parts sulfur.

5- -parts ZnO .15 p tetra methyl thiuram disulfide .75 part dibetanaphthyl nitroso-amine produced scorching in about 72 minutes: Underlike conditions the same compoun without the dibetanaphthyl nitroso-aminwas scorched in twenty minutes.

A third compound, having theformula :1 v

100 parts rubber (smoked sheet) 3 parts sulfur Parts Z 10 .15 parttetramethyl thiuram 1110110- A sulfide I v V .75 part dibeta naphthylnitroso-amine 40.5 parts carbon blacking compounds and searching tookplace in 118 minutes, while the same compound, without dibeta naphthylnitroso-amine, was scorched in about minutes, under the same conditions.

This test, developed for the purpose, serves to measure the degree ofthe retarding or was treated in the same way as the preced -v cinhibiting effect of the inhibiting compound upon the vulcanizationreaction and the ac- 'celerating influence of the ultra accelerator attemperatures of about 100 C. .orless-as contrasted with vulcanizingtemperatures which as ordinarily employed are above 120 C. Similartestswere carried out employing the same composition, but with a difi'erentlot of smoked sheet rubber which tended to scorch slower (without theaddition of prehibitor)" than the rubber employed above. The resultsobtained are given below:

' TableI scrocx Rubber -L 100 Sulfur- 1 3 Zinc oxide 5 Tetramethylthiuram disulfidefln; 0.15

Minutes before scorchin J Stock without prehibitor 44 With addition of0.75 part of:-

Diphenyl nitroso-amine 110 Dialpha naphthylnitroso-amine 62 Phenyl alphanaphthylnitrosoamme i 93 Phenyl beta naphthylnitroso-am- 1ne 93Diorthotolyl nitroso-amine .97

Phenylorthotolyl nitroso-amine 102 Phenylparatolyl nitroso-amine 102,Benzyl phenyl nitroso-amine 52 Methyl phenyl nitroso-amine 57 Diethylnitroso-amine 55- Piperidine nitroso-amine 55- c Carbazol nitroso-amine46 In a typical application of the invention to the usual vulcanizingprocedure; rubber compounds were prepared as follows:

parts rubber 5.0yparts Z'nO 8.0 parts sulfur 5.0 parts mineral rubber3.0 parts stearieacid 8 m mercapto benzo thiazole part aiphenyl'nitroso-amine Same as Formula I with-addition of 1 .0 I

i fll'o stituted nitroso-amines are especially eflec- 231 3; tive, withrespect to the prevention of presmck Pomids 300% 500% lbs. per on ilimature acceleration or vulcanization, the

' Pressure f alkyl or dialkyl substituted nitroso-amines may also beused, although somewhat less ab 70 60 675 1870 3350 690 fi ti 38 i 3%3 iCompounds which are in some respects re- 712 lated to thesubstitutednitroso-amines above g2 38 "53g 33g 33 32 defined, and have been thustested for use in 20 1055 2820 4220 e40 accordance with the invention,nclude car- 75 75 2 655 ba zole nitroso-am-ine which may be spoken of88. Q gig 318% as nitroso N -carbaz'ole, 90 20 l, 90 20 N-NO A B o 1) YY 1 e Carbazole nitroso-amlne or nltroso 'N-car- 20 gn d h ts 128 128 110g bazol'e, however, is not strictly inthe same at on no 4 Mineralrubber 5' 5 a 5 5 category with the other compounds tested and g g 3 g gg g in fact shows but little retardingefi'ect 1n 'lS\Zearie ci% t lh. .1-I g 38 38 38 the scorchlng test. The plperldlne n trosoe'rcapo enzoZROB l l Dlalpha naphthy] nitmso-amin 0 M5 0 0 amine likewise does notmanifest pronounced 3 55;; g s 'f ggg gg g 3 8 8 retarding effects. Theresults are given,

"""""" T however, because they are related to the other nitroso-aminecompounds. Their failure to Cm Final Final be more effective-1n theserespects may be attensile elcingatrlbutedto the valence linkage betweenthe R stack 300% 500% lbs per tion in I i 30 Mm 110. sqjim. ,percem andR groups of the nitroso-amine; which De Wlll be apparent from theformula of the 60 20 858 3660 66o former compound, as above given so 20770 2120 3620 680 While the above disclosure relates to a preg3 33 gig rfer-red procedure, according to the invention, 75 20 925 2400 3975 666and to specific reagents-employed 1n spec fic '75 20 832 2360 3820 660proportions, 1t is to be understood that varia- 3;? 333 28 3 253 tlonsmay be made n both the mode of carry- 90 20 1040 2560 m0 675 mg out theinvention and in the nature and go 20 5 2628 ggeg gig amount of theseveral reagents used, accord- 3 5 8 l 1050' 3820 mg to the particularconditions of practice and the characteristics desired in the result- I55 invention not 'onl may extremely active ac- 60 an milled withoutinitiating premature vul- From the data thus obtained it is to be obingProduct, as will be clear t0 skilled n served that, not only are therubber comthe I of iP rllbber'h pounds prepared with an addition of thedifThls h as gg Y o my app ica 10Il eria o. e 45 phenyl mtroso amme forexamp free from December 3, 1928,;1nd is designated as Case the tendencytoward preliminary vulcaniza- I i tion or 'scorehin but that whenvulcanized 11-5 of a group 0 cnt1.nuat1n apphcatlons filed on even dateherewith.

'at 20 pounds steam pressure and for the periods of time indicated, thevulcanized prod- I clam '5 net exhibits as good or in some instances asu- 'i l z .vulcafmzmg Fe 9 rubber 5- perior cure (with respect tointermeglate and composlttons Wlth a vulcamzmg agent and an organicaccelerator characterized by cong g ifi g fifg ffi gi i g i fi iz 5:31:trolling the action of the accelerator with an I aryl beta naphthylnitroso-amine. i It is therefore shown that by means of this 1 2. Methodof Vulcanizing rubber or rubber 12o compositions with a vulcanizingagent and an organic accelerator characterized by controlling the actionof the accelerator with 'phenyl beta naphthyl nitroso-amine.

, 3. Method of vulcanizing rubber or rubber canization, but'the'vulcanized rubberproduct compositlons Y P a-V111ca mZing agent and a I vis initially as good or better than rubber simiph -c g g acceleratorlarly compounded and vulcanized but withactenze'd/by controlling theaction of the 'ac-' out the addition of an inhibiting reagent. celeratorwith an aryl beta 'naphthyl nitroso 65 It is also indicated that whereasdiatyl subamine. v j I y 'celerators, (whic have been hithertounavailable for use in the rubber industry on ac- .7 count of their veryhigh activity) be safely em loyed in rubber compounds andmixed 15 TableVI 1 .4. Method of vulcanizing rubber or rubber com ositions with avulcanizing agent and a sulp ur-containing organic acceleratorcharacterized by controlling the action of the ac- 5 celerator withphenyl beta naphthyl nitrosoamine.

5. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and an accelerator containing a thiazole nucleuscharacterized by controlling the action of the accelerator with an arylbeta naphthyl nitro-' so-amine.

6. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and an accelerator containing a thiazole nucleuscharacterized b controlling the action of the accelerator wit phenylbeta naphthyl nitroso-amine. v E

7. Method of vulcanizing rubber or rubber compositions with avulcanizing agent and mercapto benzo thiazole characterized bycontrolling the action of the accelerator with an aryl beta naphthylnitroso-amine.

8. Method of vulcanizing rubber or rubber compositions with awulcanizing agent and mercapto benzo thiazole characterized bycontrolling the action of the accelerator with phenyl beta naphthylnitroso-amine.

9. An accelerator composition comprising an organic accelerator and anaryl beta naphthyl nitroso-amine.

10. An accelerator composition comprising an organic accelerator andphenyl beta napthyl nitroso-amine.

5 11. An accelerator composition comprising a sulphur-containing organicaccelerator and an aryl beta naphthyl nitroso-amine.

12. An accelerator composition comprising a sulphur-containing'organicaccelerator and 40 phenyl bet'a naphthyl nitroso-amine.

13. An accelerator composition comprising an accelerator containing athiazole nucleus and an aryl beta naphthyl nitroso-amine.

14. An accelerator composition comprising an accelerator containing athiazole nucleus and phenyl beta naphthyl nitroso-amine.

15. An accelerator composition comprising mercapto benzo thiazole and anaryl beta napht yl nitrosoi-amine.

16. An accelerator composition comprising merca to benzo thiazole andphenyl beta nagh l nitroso-amine.

, igned by me at Boston, Massachusetts,

this 1st day of June 1929.

. HENRY B. MOR SE.

